Many methods, for example, carrier linking, crosslinking and absorption, have been proposed to effectively immobilize enzymes in/onto fibers having a three-dimensional network structure. With the advance of nanotechnology and increasing demand for nanobiotechnology electronics since the late 1990's, new enzyme immobilization methods have been needed and numerous results thereon have been presented. Based on the results, nanostructured materials have been developed. Under such circumstances, enzyme immobilization has received a great deal of attention for its applicability in biosensors, biofuel cells, enzyme columns, ELISA kits, bioremediation devices, antifouling agents, and ibuprofen production, etc.
An important key for the commercialization of immobilization of enzymes in/onto three-dimensional network structured fibers is how to maintain the stability of the enzymes while achieving high electrical performance. To this end, various nanostructured materials have been considered, for example, nanoporous materials, electrospun nanofibers and nanoparticles with large surface areas that prevent enzymes from leaching or falling out to maximize the loading of the enzymes when the enzymes are immobilized thereinto.
Enzyme immobilization methods using porous silica are divided into two methods, i.e. simple enzyme adsorption, and crosslinking after enzyme adsorption. The latter method provides better results in terms of stability than the former method, but there is no significant difference in activity between both methods because similar amounts of enzymes are adsorbed into silica. According to conventional methods for increasing the amount of enzymes immobilized into nanofibers, functional groups present on the surface of the nanofibers are covalently bonded to the enzymes, and crosslinkers are used to coat the enzymes on the nanofibers. However, the enzymes are immobilized in only limited amounts and are prone to denaturation. Another problem is that it is difficult to apply the methods to nanofibers having no surface functional groups capable of covalently bonding to the enzymes.
Consequently, the conventional methods for immobilizing enzymes in/onto three-dimensional network structured fibers have disadvantages of very low yield and poor long-term stability. Due to these disadvantages, the conventional methods are extremely difficult to commercialize.